1. Field Of The Invention
The present invention relates generally to the art of refrigeration. More particularly, this invention is directed to the use of a basic heat pump refrigeration circuit to additionally accomplish the heating of a liquid. With still more particularity, my invention is directed to a highly flexible refrigeration circuit operable in at least four modes which provides for the cooling of a space or the heating of a space or the heating of a liquid or for the simultaneous cooling of a space and heating of a liquid. Finally, this invention relates to a refrigeration circuit operable in multiple modes in which refrigerant charge control problems commonly associated with such circuits are alleviated by the selective incorporation of a refrigerant charge reservoir into the circuit when the circuit is called upon to heat the liquid.
2. Background Art
Commonly available devices known as heat pumps are reversible refrigeration systems capable of conditioning a space by heating or cooling the air within the space. The use of heat pump systems to additionally provide for the heating of a liquid utilizing heat otherwise rejected as waste heat has previously been proposed and the efficiency of so utilizing a heat pump system has been recognized. U.S. Pat. Nos. 3,916,638 and 4,249,390 both disclose basic heat pump systems modified to provide domestic hot water heating in addition to space conditioning. The former discloses a multi-mode water-to-air heat pump refrigeration circuit in which the water heating heat exchanger is bypassed when the system is in a space heating mode. The latter discloses a water-to-air heat pump refrigeration circuit in which the system compressor discharges directly to the heat exchanger utilized to heat water. The latter suggests that under certain conditions water may be heated while a space is being heated and also contemplates some system for controlling the amount of water circulated from the water source which acts as a heat sink.
Refrigerant charge control problems within such systems are significant, well recognized and cannot be ignored. U.S. Pat. No. 3,994,142 is directed at a solution for refrigerant charge control problems in a refrigeration circuit in which at least one heat exchanger is operated only intermittently. The solution contemplates flooding the intermittently operated heat exchanger with liquid refrigerant to avoid the problems associated with attempting to evacuate and isolate that heat exchanger. Refrigerant charge control problems are likewise noted in U.S. Pat. No. 4,299,098, a patent assigned to the assignee of the invention herein disclosed. Refrigerant charge control is accomplished in the latter patented circuit by venting the inactive heat exchanger to the suction port of the system compressor in order to evacuate the inactive heat exchanger and provide refrigerant charge control within the system.
A multi-mode refrigeration circuit is needed which is simpler yet equally flexible and effective as previous circuits in order to make practical the use of the readily available waste heat in heat pump systems to heat liquids such as water for domestic purposes.